The French Senate is proposing a 15% capital gains tax on property whose value increases as a result of new transport networks that form part of the Grand Paris plan for transformation of the Greater Paris area. But five property groups said such a tax would "reduce the attractiveness of the Paris Ile-de-France region relative to other international property markets" and turn investors away from projects involved in the Grand Paris plan.

Jean-Paul Dumortier, president of listed property association FSIF (Fédération des Sociétés Immobilières et Foncières), said some areas due to benefit, such as Saclay to the south and Le Bourget to the north, are still developing and need to attract new investors, but the proposed move would turn them into high tax locations. The French property sector already faces a high tax burden relative to other industries and to other countries, the associations argue. Sellers would be likely to add the new tax onto the price of a property, thereby reducing transaction volumes.

The proposed tax is intended to help finance construction of new transport infrastructure, but the groups said it is the wrong answer to the genuine problem of financing the project. They called for urgent discussions with the government and the parliament to work out alternative solutions.